In March 1804, the Semiramis, a 120-foot schooner, was headed home to Newport, R.I., from a trade journey when it ran aground in Nantucket Sound and slowly sank.

The ship was returning from a two-year voyage from New England to South America, then the Pacific Northwest to China.

Thirty hours after striking the shoal, the Semiramis disappeared under the waves, taking with it one sailor and hundreds of thousands of dollars worth of gold, silver and Chinese porcelain, among other cargo.

Now, the shipwreck is at the center of a case in federal court involving longtime treasure hunter Barry Clifford.

Clifford's Provincetown-based company, Vast Explorer Inc., and the Massachusetts Board of Underwater Archaeological Resources were both in U.S. District Court in Boston on last week for a brief hearing on a salvaging rights lawsuit the company filed in 2009.

Vast Explorer is the same company that found and recovered artifacts from the wrecked pirate ship Whydah off the Cape in the 1980s. The board is the agency charged with overseeing underwater recovery and salvage operations in the commonwealth.

Clifford is seeking exclusive salvage rights for the Semiramis, which he says rests near Long Shoal, a sandbar in Nantucket Sound about 15 miles northwest of Nantucket between that island and Martha's Vineyard.

"I became interested when I learned it was one of the early 'China traders,'" Clifford said in a recent interview.

The exact location of the Semiramis, however, is a point of contention between him and the state.

In the hearing Dec. 5, Magistrate Judge Robert B. Collings ordered that Vast Explorer survey the alleged site this spring and report its findings to the court in June, according to court documents.

Right now, it appears that the wreck could be in an area right on the dividing line between state and federal waters, according to charts and coordinates in court files.

The difference could mean extra work and additional costs for Clifford as he moves forward with a recovery effort, but wouldn't affect whether the ship could be excavated.

It would, however, make a difference to the commonwealth since under state law, the board is entitled to 25 percent of any items recovered in state waters, Victor Mastone, the board's director and chief archaeologist, said.

Clifford said he has no plans to sell any of the things he salvages. Instead, they would become part of a shipwreck museum he hopes to open in Hyannis. He also said he plans to give the state 25 percent, no matter where the ship is found.

"We have a good relationship with the Massachusetts board, and we want to continue to have a good relationship with them," he said.

The vessel is one of the earliest China traders — New England ships that traded with the Far East to boost American exports following the Revolutionary War, said Ken Kinkor, Vast Explorer's project historian and director of research.

"It's ships like this that laid the groundwork for New England trade supremacy," he said.

The Semiramis remained undiscovered until 1978, when Clifford saw a pair of wooden hull sections while diving in the area with the late John F. Kennedy Jr., he said. The sections were about 1½ miles apart and appeared to be similar in construction. Clifford also observed a debris trail between the two, according to court documents.

During the dive, he recovered an undisclosed amount of "ceramic material" that was "consistent with 'Lowestoft-style' porcelain produced in Canton, China, for the export trade to Europe in the 18th century," according to court documents. Canton, a city in southern China, is now known as Guangzhou.

The experience left a lasting impression with Clifford.

"It's really one of things that got me started in this field," he said.

Vast Explorer applied for a state permit to document the wreck site on Aug. 27, 2009, following anecdotal reports that a hurricane had blown away the sand cover and exposed portions of the wreck to looting, according to court documents.

In that filing, the company listed 11 coordinate points that it says formed the boundary of the wreck site. A portion of those points lie within the three-mile limit of state jurisdiction.

Days later, the company filed suit in U.S. District Court seeking exclusive salvage rights. That filing lists four coordinate points that sit completely outside the first boundary in waters controlled by the federal government.

In 2010, the company put out a mandatory notice for anyone with an interest in the ship to come forward, according to court documents.

The commonwealth then filed its grievances, stating that Clifford had given two separate sets of coordinates for the wreck. The board also contested whether Clifford has positively identified the wreck, given that there are several similar lost vessels in the area, according to court documents.

The location of the ship is the deciding factor as to what law applies. If in federal waters, the court must decide whether to award salvage rights and title to the plaintiff, Clifford, in accordance with applicable laws, said Ole Varmer, an admiralty law expert with the National Oceanographic and Atmospheric Administration.

This can come with certain requirements, depending on the circumstances surrounding the wreck, he said. This also means a potential salver, or salvager, doesn't have to go through a complex permitting process required by the state.

"It's not so much that there's a benefit for a salver in federal waters; it's just the number of laws that apply," he said.

Mastone declined to comment on the specifics of the lawsuit, but spoke generally about state salvage laws.

For artifacts to be recovered in state waters, the salvaging party must apply for a series of permits. The first, called a "reconnaissance permit," grants the applying party exclusive rights to a wreck if they can pinpoint its location and prove that it's the vessel they say it is, he said.

Once a wreck site is satisfactorily documented, the party can apply for a "salvaging permit," which allows it to go forward with any kind of artifact recovery and excavation of a site. To do this, the reporting party must either be an archaeologist or employ one, he said.

Once complete, the board must sign off before the recovered items are divided up, Mastone said.